Climate Change & Society Midterm
What're RCPs and SSPs?
Representative Concentration Pathway (RCP) is a greenhouse gas concentration trajectory adopted by the IPCC. The pathways describe different climate futures. The RCPs - originally RCP2.6, RCP4.5, RCP6, and RCP8.5 - are labelled after a possible range of radiative forcing values in the year 2100 (2.6, 4.5, 6, and 8.5 W/m 2, respectively). Shared Socioeconomic Pathways (SSPs) are scenarios of projected socioeconomic global changes up to 2100. They use the same concept of radiative forcing values as in RCP. The scenarios are:SSP1: Sustainability (Taking the Green Road)SSP2: Middle of the RoadSSP3: Regional Rivalry (A Rocky Road)SSP4: Inequality (A Road divided)SSP5: Fossil-fueled Development (Taking the Highway)
The long-term goal of Paris Agreement
Responding to that objective, the Paris Agreement (2015) established the long-term goals of 'holding the increase in global average temperature to well below 2°C above pre- industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels' and of achieving 'a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century'.
What are the main five components of uncertainties in future climate projections? (10 points)
Response uncertainties internal variable uncertainties radiative forcing interaction uncertainties Model uncertainties
Definition of sea ice extent and sea ice area
Sea ice extent: The total area of all grid cells with at least 15% sea ice concentrationSea ice area: the actual area of the ocean covered by sea ice
Radiative forcing
a measure of the net change in the energy balance in response to anexternal perturbation
Provide examples of positive and negative feedbacks in climate system and explain
Water vapor has positive feedback in the climate system. An increase of water vaporleads to an increase in temperature. The increase in temp causes more water vapor toform. Similarly, the peat and permafrost decomposition is a positive feedback loop. As 2the permafrost thaws, the organic matter is released and breaks down into carbon dioxideor methane. This increases the temperature, thus thawing more permafrost.On the other hand, air-sea CO2 exchange is a negative feedback loop. An increase inCO2 concentration increases the land and ocean's carbon uptake. This mitigates thegrowth rate of CO2 on the atmosphere. Another negative feedback loop is lapse rate.Lapse rate decreases in respect to increase greenhouse effects.
Definition of weather and climate. What's the main difference?
Weather describes the conditions of the atmosphere at a certain place and time with reference to temperature, pressure, humidity, wind, and other key parameters (meteorological elements).Climate the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years.
The reason of the seasonal trend of CO2
When plants are growing, photosynthesis outweighs respiration. As a result, plants take more CO2 out of the atmosphere during the warm months when they are growing the most. This can lead to noticeably lower CO2 concentrations in the atmosphere.
The number of years used to describe climate in World Meteorological Organization
30 years - World Meteorological Organization
The main four sources of greenhouse gas monitoring (NASA, NOAA, SIO, UCI)
AGAGE = Advanced Global Atmospheric GasesExperiment (1978, Sponsored by NASA'sAtmospheric Composition Focus Area in EarthScience)NOAA/ESRL/GMD = National Oceanic andAtmospheric Administration, Earth SystemResearch Laboratory, Global Monitoring DivisionSIO = Scripps Institution of Oceanography,University of California, San Diego (late 1950s)UCI = University of California, Irvine, Department of Chemistry
The two main processes responsible for glacier size change
AccumulationAblation
Glaciers definition
All perennial surface land ice masses outside of the Antarctic and Greenland ice sheets.
What is emergent constraint?
An emergent constraint is the relationship between an uncertain aspect of future climatechange and an observable feature of the Earth System.
Baseline
Baseline refers to a period against which differences are calculated
The cause of CFC-12 decline
CFCs were phased out via the Montreal Protocol due to their part in ozone depletion.
What are the trends of capabilities for observing the physical climate system?
Capabilities for observing the physical climate system have continued to improve and expand overall, but some reductions in observational capacity are also evident (high confidence).Surface-based networks have reduced in their coverage or range of variables measured due to COVID-19 and other factors.Ship- based measurements, which are important for ocean climate and re-analyses through, have been in decline due to the number of ships contributing observations.Satellite frequencies (e.g., 5G frequencies overlap with water vapor measurements).The loss of natural climate archives.
What is responsible for the decreased aerosol loadings in US?
Clean Air Act: adopted in 1970, amended in 1977and 1990Mandates:- Cars to be equipped with catalytic converters (toconvert carbon monoxide and hydrocarbons intocarbon dioxide and water) Installation of scrubbers insmokestacks.
What are the two ways IPCC represent uncertainties?
Confidence in the validity of a finding, based on the type, amount, quality, and consistency of evidence (e.g., data, mechanistic under-standing, theory, models, expert judgment) and the degree of agreement. Confidence is expressed qualitatively. The IPCC represents uncertainty by representing level of uncertainty by data stated. ex. : High agreementMedium evidence 1. by level of agreement 2. By amount of evidence
What is CMIP6?
Coupled Model Intercomparison Project
What is DTR and what is the trend?
Diurnal Temperature Range (DTR)
The trend of global ocean carbon uptake
From a process point of view, the ocean uptake of anthropogenic carbon is a two-step set of abiotic processes that involves the exchange of CO 2 , first across the air-sea boundary into the surface mixed layer, followed by its transport into the ocean interior where it is stored for decades to millennia, depending on the depth of storage.Total: 155 Pg C (1750-2010)
Tidewater glaciers
Glaciers that terminate in the sea
What is GMST and GSAT?
Global mean surfacetemperature (GMST) Global surface airtemperature (GSAT)
•Global relative humidity is increasing over the recent decades. (T/F)
F
•The melting of sea ice will increase sea level. (T/F)
F
•There is high confidence that global streamflow is decreasing in recent decades. (T/F)
F
What is FAR, SAR, TAR, AR4, AR5 and AR6?
First Assessment Report, Second Assessment Report, Third Assessment Report, 4th Assessment Report, 5th Assessment Report, and 6th Assessment Report.
Gauge (confounding factors) and satellite measurements of sea level
For gauge measurements: Ocean volume change and vertical land motion (VLM)Glacial isostatic adjustment (GSA) is the ongoing movement of land once burdened by ice-age glaciers. Tectonic activityGroundwater mining induced land subsidence
What are the main five components of uncertainties in future climate projections?
For observations:Inherent randomness, instrument biasFor future projections:Radiative forcing uncertaintyClimate response uncertaintyNatural and internal climate variationsInteractions between variability and radiative forcings Model uncertainty (not model spread)AR6 Foundations and ConceptsUncertainties
Why we cares about the variability of the climate signal?
Natural variations can temporarily mask or change anthropologic changes in climate
Frozen ground temperature trend
Permafrost:Wherever the ground remains at or below 0 degree Celsius for at least two consecutiveyears, it is called permafrost.Seasonally frozen ground is a soil layer that freezes and thaws annually, which may ormay not overlie terrestrial permafrost, and also includes some portions of the Arcticseabed that freeze in winter.Seasonally Frozen Ground:Active-layer thicknessThe active layer thickness (ALT) is defined as either the maximum thaw depth at the endof the summer thaw season or the maximum depth of the 0 °C isotherm.
What's PSS78?
Practical Salinity Scale 1978 (PSS78) PSS-78 is based on an equation relating salinity to the ratio of the electrical conductivity of seawater at 15°C to that of a standard potassium chloride solution (KCl).
What are the trends of solar and volcanic aerosol forcings in the last 2000 years?
Solar activity since the late 19th century was relatively high but not exceptional in thecontext of the past 9 kyr (high confidence). The associated global mean effective radiativeforcing is in the range of -0.06 to +0.08 W m -2 .The average magnitude and variability of volcanic aerosol forcing since 1900 are not unusualin the context of at least the past 2.5 kyr (medium confidence).
Definition of specific humidity and relative humidity
Specific Humitity-The weight (amount) of water vapor contained in a unit weight (amount) of air. Itis usually expressed as grams of water vapor per kilogram of air. Relative humidity-The ratio of the amount of water present in the air to the amount present at saturation.
Dobson unit
Stratospheric O 3 concentrationis expressed in Dobson units.- If all stratospheric O 3 molecules were uniformlydistributed around the globe, they would make alayer 3 mm thick (at 0 oC and 1 atm, standardtemperature and pressure or STP).
•CFC-12 is decreasing over the recent two decades. (T/F)
T
The difference between troposphere and stratosphere ozone
Unlike stratospheric ozone, which forms naturally in the upper atmosphere and protects us from the sun's harmful ultraviolet rays, ground-level (or tropospheric) ozone is created through the interactions of man-made (and natural) emissions of volatile organic compounds and nitrogen oxides in the presence of heat
What is IPCC and what is the role of IPCC?
The Intergovernmental Panel on Climate Change(IPCC) is the United Nations body for assessingthe science related to climate change.... to assess on a comprehensive, objective, open and transparent basis thescientific, technical and socio-economic information relevant to understandingthe scientific basis of risk of human-induced climate change, its potentialimpacts and options for adaptation and mitigation.""IPCC reports should be neutral with respect to policy, although they may need todeal objectively with scientific, technical and socio-economic factors relevant tothe application of particular policies."
The main energy pathways on Earth
The Sun provides itsenergy to the Earthprimarily in the tropicsand the subtropics; it'sthen redistributed tomiddle and highlatitudes by atmosphericand oceanic transportprocesses
Frozen ground active depth trend
The active layer thickness (ALT) is defined as either the maximum thaw depth at the endof the summer thaw season or the maximum depth of the 0 °C isotherm.
Anomaly, why anomaly is often used to present climate trends?
Variations in observed and simulated climate variables over time are often presented as 'anomalies', that is, the differences relative to a baseline, rather than using the absolute values.
Definition of cryosphere and why it is important in global climate
The cryosphere is the collective term for the components of the Earthsystem that contain a substantial fraction of water in the frozen state(Table 4.1). The cryosphere comprises several components: snow, riverand lake ice; sea ice; ice sheets, ice shelves, glaciers and ice caps; andfrozen ground which exist, both on land and beneath the oceans (seeGlossary and Figure 4.1). The lifespan of each component is very differ-ent. River and lake ice, for example, are transient features that general-ly do not survive from winter to summer; sea ice advances and retreatswith the seasons but especially in the Arctic can survive to becomemulti-year ice lasting several years. The East Antarctic ice sheet, on theother hand, is believed to have become relatively stable around 14million years ago (Barrett, 2013). Neverthe
The major components of cryosphere
The cryosphere plays a major role in the Earth's climate system through its impact on the surface energy budget, the water cycle, primary productivity, surface gas exchange and sea level.The cryosphere is a natural integrator of climate variability and provides some of the most visible signatures of climate change.
What determines sea surface salinity pattern?
The factors affecting salinity o The horizontal salinity distribution of the upper ocean largely reflects the exchange between ocean and atmosphere. o Ocean circulation also affects the regional distribution of surface salinity. o Melting and freezing of ice (both sea ice and glacial ice) also influence ocean salinity.
The importance of ocean in climate system
The ocean influences climate by storing and transporting large amounts of heat,freshwater, and carbon, and by exchanging these properties with the atmosphere.o >90% of the excess heat energy stored by the Earth over the last 50 years isfound in the oceano >75% of the total exchange of water between the atmosphere and the Earth'ssurface through evaporation and precipitation takes place over the oceanso The ocean contains 50 times more carbon than the atmosphereo Absorb about 30% of human emissions of carbon dioxide
Changes in streamflow
The sign of global streamflow trends remainsuncertain, with slightly more globally gauged riversexperiencing significantly decreasing flows thansignificantly increasing flows since the 1950s (lowconfidence).
The two key factors affecting sea level increase
Thermal expansion Melting of ice
Does UHI play a significant role in global land surface air temperature?
little to no effect
Why dry-air based ppm, ppt units were used to describe gas concentration in IPCC reports?
presence of water vapor does not give most accurate results, use of dry air is more accurate
What is Argo? Why is important?
the broad-scale global array of temperature/salinity profiling floats, is a major component of the ocean observing system
Reference period
reference period is used more generally to indicate a time period of interest, or a period over which some relevant statistics are calculated.
Be able to explain the CO2, CH4 and N2O trends
slides 7,8 9,10,11 lecture 4 overall increase
